Chpt. 42: Human Reproduction

1. Chpt. 42: Human Reproduction

2. Organisation • Both the male and female reproductive system are composed of: • a pair of structures to produce sex cells. • a series of transport tubes • glands which secrete hormones

3. Male Reproductive System LS

4. The Male Reproductive System • Main Parts: • Testes • Scrotum • Epididymis • Sperm Duct (vas • deferens) • Associated Glands • Sperm • Penis

5. The Male Reproductive System • Testes (Testis): • consists of a coiled mass of tubules • produces sperm by meiosis • makes testosterone (hormone) • Scrotum: • contains the testes • temperature in scrotum is35o C i.e. below body temperature. • Epididymis: • located outside each testis • stores and matures sperm cells

6. The Male Reproductive System • Sperm Duct (vas deferens): • transports sperm from the testes to the urethra • Note:urethra is tube located in centre of penis and is responsible for carrying urine or sperm out of body) • Associated Glands: • Seminal Vesicles – provides liquid for sperm to swim • in and produces fructose which gives sperm energy • Prostate Gland – produces liquid to nourish sperm • Cowper’s Gland – produces a fluid to lubricate the urethra • Note: when seminal fluid is added to sperm cells the resulting liquid is called semen.

7. The Male Reproductive System • Sperm (Spermatozoa): • Sperm are produced by meiosis in the testes • sperm are haploid cells i.e. they only contain 23 chromosomes.

8. The Male Reproductive System • Penis: • carries sperm into the female reproductive system. • swollen tip of penis called glans. • foreskin (fold of skin) partially covers the glans.

9. The Male Reproductive System • Male Hormones: • At puberty: two hormones are produced by the male pituitary gland: • FSH(Follicle Stimulating Hormone): stimulates the sperm-producing cells in the testes to divide by meiosis and produce sperm. • LH (Luteinising Hormone): stimulates the production of testosterone in the testes. • Before puberty: the testes produce small amounts of the hormone testosterone. • Testosterone: causes primary and secondary male characteristics.

10. Sexual Characteristics • Primary sexual characteristics: are the growth of reproductive organs. • Secondary sexual characteristics: are the features that distinguish males from females apart from the sex organs themselves. • Secondary male characteristics: • growth of pubic, facial and body hair • enlargement of larynx • growth spurt • widening of the shoulders • increased sebum production – acne • increased muscular and bone development

11. Infertility • Infertility is the inability to produce offspring • Male infertility: - Low Sperm Count • Cause: - persistent smoking of cigarettes • - alcohol abuse • - use of marijuana or anabolic steroids • - low levels of male hormones • - mumps in adult life • Treatment: • changes in diet and lifestyle i.e. no smoking, no drugs, reducing alcohol intake, reducing stress levels. • Hormonal therapy • In-vitro fertilisation

12. Female Reproductive System LS

13. The Female Reproductive System • Main Parts: • Ovaries • Fallopian Tubes • Uterus (womb) • Cervix • Vagina

14. The Female Reproductive System • Ovaries: • produces eggs (ovum) by meiosis • produces female hormones • after puberty (11-12 yrs.) approx. 20 eggs produced by meiosis each month – only 1 survives. • This haploid egg is surrounded by a Graafian follicle which produces the female hormone oestrogen. • This Graafian follicle matures on the surface of the ovary and bursts at ovulation to release the egg. • After ovulation this follicle becomes the corpus luteum – secretes the hormone progesterone.

15. The Female Reproductive System • Fallopian Tubes: • moves egg down tube by cilia and muscular peristalsis. • site of fertilisation • funnel of Fallopian tube catches the egg after ovulation. • Oviduct : Fallopian tubes and uterus.

16. The Female Reproductive System • Uterus (Womb): • lined with the endometrium which nourishes the embryo. • Cervix: • opening into the uterus. • Vagina: • muscular tube which allows entry of sperm into the female system • birth canal

17. The Female Reproductive System • Vagina: • Labia – folds of skin which protect vagina and are collectively known as the vulva. • Hymen – ring of tissue which may partially block the vagina entrance.

18. The Female Reproductive System The Menstrual Cycle • The menstrual cycle is a series of changes that happen about every 28 days in the female body. • The menstrual cycle takes place: • between puberty and the menopause • only when a female is not pregnant

20. The Female Reproductive System • Main events in the average menstrual cycle: • Days 1 to 5: • If fertilisation does not occur blood and tissue from the inner lining of the uterus (endometrium) is released – Menstruation (period). • Meiosis in ovary produces new egg which becomes surrounded by Graafian follicle. • Days 6 to 14: • Graafian follicle produces oestrogen, causing the endometrium to thicken.

21. The Female Reproductive System • Main Events in the Menstrual Cycle • Day 14: • Ovulation occurs – this is the release of an egg from the ovary • Egg passes into the funnel of the fallopian tube. • Endometrium continues to thicken. • Day 14 – 28: • Graafian follicle develops into corpus luteum and produces progesterone. • Progesterone causes endometrium to thicken even more and prevents new eggs forming.

22. The Female Reproductive System • Main events in the Menstrual Cycle • If fertilisation has not occurred: • around day 22 corpus luteum begins to break down. • Progesterone levels decrease, causing endometrium to break down. • Menstruation and cycle begins again.

24. The Female Reproductive System • Female Hormones: • Oestrogen: • - causes endometrium to thicken in first half of cycle. • - at puberty high oestrogen levels cause the primary female sexual characteristics. • - prevents eggs from developing. • Progesterone: • - causes the endometrium to thicken for the last 14 days. • - prevents eggs from developing. • Combination of oestrogen and progesterone at puberty: • - causes secondary female characteristics.

25. Sexual Characteristics • Secondary Female Characteristics: • Growth of pubic and underarm hair • widening of hips • maturing and enlargement of breasts • increased body fat • growth spurt

26. Infertility Female Infertility: - The failure to release eggs i.e. ovulate Cause: - hormonal disorder (endocrine gland failure) i.e. failure to produce FSH – no eggs failure to produce LH – no ovulation - stress - tumour on ovary - no obvious cause Treatment:- for hormonal disorder- hormonal treatment. - reduce stress - surgery on the ovary - in-vitro fertilisation

27. Hormonal Control of Menstrual Cycle (Higher Level Only) • Four hormones are involved in the menstrual cycle: • - 1. FSH – follicle stimulating hormone • - 2. Oestrogen • - 3. LH – luteinising hormone • - 4. Progesterone

28. FSH: • - produced by the pituitary gland • - produced early in cycle – days 1 – 5 • Oestrogen: • - produced by the graafian follicle • - produced from days 5 – 14 • - causes the endometrium to develop and inhibits FSH production • - increased levels of oestrogen at day 14 cause LH to be produced • FSH causes eggs to develop which are surrounded • by graafian follicles • Graafian follicles secrete oestrogen (indirectly FSH • controls oestrogen production)

29. 3. LH: - produced by the pituitary gland. - produced on day 14 - it causes ovulation to occur and the remains of the graafian follicle to become the corpus luteum 4. Progesterone: - produced by the corpus luteum - produced from days 14 to 28 - maintains the structure of the endometrium - inhibits the production of FSH and LH - prevents contractions of the uterus

30. If pregnancy does not occur the corpus luteum breaks down – day 22 Day 28 – as a result of low levels of progesterone and oestrogen the following happens: - FSH secretion is no longer inhibited - new eggs begin to develop - uterus contracts and endometrium is shed from the body - menstruation

31. Menstrual Disorder – Fibroids • Fibroids are benign tumours of the uterus. • Cause: unknown although may be associated with • oestrogen levels • Treatment: • - small fibroids frequent check ups • - large fibroids – surgery • - large no. of fibroids – possible hysterectomy Symptoms: none when small but when large cause prolonged periods, pain, heavy periods, miscarriage, infertility

32. Sexual Intercourse (Copulation) • Common Level • Copulation (sexual intercourse): is where the erect penis of the male is placed in the vagina of the female. • Stages of Copulation: • Sexual Arousal: • - in the male blood flow into penis increases and out of penis decreases – penis becomes erect • - in the female vagina becomes enlarged and produces lubricants • Copulation (Coitus or sexual intercourse): • - penis moves inside the vagina • - breathing and heart rates increase

33. Sexual Intercourse 3. Orgasm: - is the climax of sexual excitement. - in the female the outer vagina and uterus contract - ejaculation occurs – this is the emitting of semen from the penis. 4. Behaviour of sex cells: - insemination occurs – this is when semen is released into the vagina just outside the cervix. - sperm is pushed to an egg (if present) in fallopian tube. - if egg present it releases a chemical attracting the sperm – chemotaxis.

34. Fertilisation • Fertilisation: occurs when the nucleus of the sperm fuses with the nucleus of the egg, forming a diploid zygote. • normally takes place in the fallopian tube. • many sperm swarm egg but only one enters egg • upon entering sperm loses its tail and the membrane of the egg undergoes a rapid chemical change forming a fertilisation membrane • This membrane prevents other sperm from entering.

35. Fertilisation Fertile Period • Sperm can survive in female reproductive system for up to 3 days therefore pregnancy can occur if female has intercourse 3 days before ovulation. • Egg can survive for 2 days therefore pregnancy can occur if female has intercourse 2 days after ovulation. • As a result, in a typical menstrual cycle fertile period lasts from day 11 to day 16. • Due to irregular menstrual cycles the fertile time is really days 9 to 18

36. Birth Control • Birth Control: involves taking steps to reduce the number of children born. • Abortion: involves the termination of a pregnancy. • Contraception: is the deliberate prevention of fertilisation or pregnancy. There are four methods: • Natural • Mechanical • Chemical • Surgical Abortion Contraception

37. Birth Control • Natural Contraception: involves not having intercourse around the time of ovulation. • natural methods of contraception try to identify the time of ovulation based on: • - body temperature • - mucous secreted in the cervix • - past menstrual cycles (rhythm method) • Mechanical Contraception: involves using physical barriers to prevent sperm reaching egg. • condoms • diaphragms • caps

38. Birth Control • Chemical Contraception: involves the use of spermicides or hormones. • Vaginal spermicides • The pill • Surgical Contraception: involves sterilisation of the female and vasectomy for males. • Tubal Ligation • Vasectomy

40. Implantation • Implantation: is the embedding of the fertilised egg into the lining of the uterus. • occurs 6 to 9 days after fertilisation • during implantation amnion develops around the embryo • amnion secretes amniotic fluid which protects the embryo.

42. Early Development of the Zygote • Higher Level Only • Fertilised egg contains 46 chromosomes • Zygote divides many times by mitosis to form a ball of • cells called the morula (after 3 days) • Approx 5 days after fertilisation and further mitosis, • morula forms a hollow ball called blastocyst • Implantation occurs – blastocyst embeds in uterus • Inner cells form the embryo and outer cells form • amnion which secretes amniotic fluid which protects • embryo • Placenta forms from embryonic and uterine tissues

43. Placenta produces hormones (oestrogen and • progesterone) and allows the exchange • of materials between mother and baby to occur – • wastes, antibodies, nutrients etc.

44. Embryonic Development • Higher Level Only • 10 days after fertilisation cells of inner cell mass of the • blastocyst form embryonic disc which gives rise to • three layers of cells called primary germ layers. • Each of these layers give rise to different tissues:

45. 4th week – heart is formed and beating • - umbilical cord formed • 5th week – internal organs and limbs have started to form • 6th week – eyes visible • - mouth, nose, ears are forming • 8th week – all major organs are formed and is now called a foetus • 12th week – eyes low and widely spaced, cartilage replaced by bone (ossification), nerve and muscle coordinate, movement of the legs & arms, sex organs distinguishable, baby teeth begin to grow, the foetus sucks its thumb and can kick, breathe and urinate

46. After week 12 the baby continues to grow • Pregnancy – Gestation: • is the length of time spent in the uterus from • fertilisation to birth ( 9 months – 40 weeks)

47. Birth Common Level • For the first 10 - 12 weeks oestrogen and progesterone • are produced by the corpus luteum, after that they are • made by the placenta • Before birth the production of progesterone stops and • oestrogen increases – walls of uterus begin to contract • Pituitary gland of mother produces hormone called • oxytocin– causes contractions of uterine muscle • resulting in onset of labour.

48. Birth • Labour may be divided into three stages: Stage 1 - foetus rotates towards cervix - cervix widens - amniotic fluid is released - contractions begin Stage 2 - contractions become stronger & more frequent - foetus is pushed head first through the vagina Stage 3 - the placenta & foetal membranes are expelled (after birth)

50. Lactation • is the production of milk by the mothers breast • (mammary glands) • prolactin produced by the pituitary gland stimulates • milk production • for first few days after birth colostrum produced from • breasts. This has less fat and sugar than breast milk but • is higher in minerals, proteins and antibodies.